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This section describes the hardware and software features of the Cisco Analog Telephone Adaptor (Cisco ATA) and includes a brief overview of the H.323 protocol.
The Cisco ATA analog telephone adaptors are handset-to-Ethernet adaptors that allow regular analog telephones to operate on IP-based telephony networks. Cisco ATAs support two voice ports, each with an independent telephone number. The Cisco ATA 188 also has an RJ-45 10/100BASE-T data port.
This section covers the following topics:
The Cisco ATA, which operates with Cisco voice-packet gateways, makes use of broadband pipes that are deployed through a digital subscriber line (DSL), fixed wireless-cable modem, and other Ethernet connections.
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Note The term Cisco ATA refers to both the Cisco ATA 186 and the Cisco ATA 188, unless otherwise stated. |
H.323 is the International Telecommunication Union (ITU) standard for transmitting voice, video, and data across an IP network. Like other VoIP protocols, the H.323 standard is designed to address the functions of signaling and session management from within a packet telephony network. Signaling allows call information to be carried across network boundaries. Session management provides the ability to control the attributes of an end-to-end call. The H.323 standard includes support for call signaling and control, multimedia transport and control, and bandwidth control for both point-to-point and point-to-multipoint conferences.
The H.323 standard includes the following protocols:
Components that the H.323 standard employs include a system of interconnected voice terminals, gateways, gatekeepers, multipoint control units (MCUs), and proxy servers. Voice terminals provide point-to-point and point-to-multipoint conference capability for audio, video, and data. Voice gateways interconnect the packetized IP network to the PSTN or ISDN network. Gatekeepers provide admission control and address translation services for H.323 voice terminals and gateways. MCUs enable two or more gateways to engage in point-to-point or point-to-multipoint audio or video conferences.
This section contains descriptions of the following H.323 components:
Voice terminals in an H.323 network must feature system control units, media transmission capabilities, audio codecs, and network interfaces suitable for transmitting and receiving packetized data.
H.323 gateways feature a mixture of characteristics of both standard Switched Circuit Network (SCN) access points and H.323 access points. Gateways perform the translation of audio, video, and data transmission formats as well as interacting with communications systems and various protocols. A primary responsibility of an H.323 gateway is the call setup and teardown necessary to complete a call to and from a packetized IP network and a standard switched network.
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Note Gateways are necessary in an H.323 system to connect calls over a packetized IP network to a switched circuit network such as the PSTN. |
Gatekeepers are primarily responsible for pre-call and call-level control services for H.323 gateways. Gatekeepers are an optional component in an H.323 system. However, if present, gatekeepers must perform the following call setup and management services:
When used in an H.323 system, gatekeepers can also (but are not required to) provide the following functionality:
MCUs are endpoints in an H.323 network that support point-to-multipoint conferences and consist of a multipoint controller and at least one multipoint processor responsible for receiving voice, video, and data streams. These streams are distributed to access points participating in a point-to-multipoint conference.
An H.323 proxy server is a proxy specifically designed for the H.323 protocol and examines packets between two communicating applications. Proxies can determine the destination of a call and perform call-connection steps, if necessary.
H.323 proxies perform the following key functions:
The Cisco ATA 186 and Cisco ATA 188 are compact, easy-to-install devices. Figure 1-5 shows the rear panel of the Cisco ATA 186. Figure 1-6 shows the rear panel of the Cisco ATA 188.
The unit provides the following connectors and indicators:
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Note The Cisco ATA186-I1 and Cisco ATA188-I1 provide 600-ohm resistive impedance. The Cisco ATA186-I2 and Cisco ATA188-I2 provide 270 ohm + 750 ohm // 150-nF complex impedance. The impedance option is requested when you place your order and should match your specific application. If you are not sure of the applicable configuration, check your country or regionaltelephone impedance requirements. |
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Note The Cisco ATA 188 performs auto-negotiation for duplexity and speed and is capable of 10/100 Mbps, full-duplex operation. The Cisco ATA 186 is fixed at 10 Mbps, half-duplex operation. |
The function button lights when you pick up the handset of a telephone attached to the Cisco ATA. The button blinks quickly when the Cisco ATA is upgrading its configuration.
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Note If the function button blinks slowly, the Cisco ATA cannot find the DHCP server. Check your Ethernet connections and make sure the DHCP server is available. |
Pressing the function button allows you to access to the voice configuration menu. For additional information about the voice configuration menu, see the "Voice Configuration Menu" section.
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Caution Never press the function button during an upgrade process. Doing so may interfere with the process and may permanently disable the Cisco ATA. |
The Cisco ATA supports the following protocols, services and methods:
The Cisco ATA supports the following voice codecs (check your other network devices for the codecs they support):
In addition to H.323, the Cisco ATA supports the following signaling protocols:
H.323 and SIP share the same software image. SCCP and MGCP also share a software image, which is separate from the H.323/SIP image. If you wish to perform a cross-protocol upgrade from H.323 to another signaling image, see the "Upgrading the Signaling Image from a TFTP Server" section.
Other protocols that the Cisco ATA supports include the following:
For a list of required H.323 parameters as well as descriptions of all supported Cisco ATA H.323 services and cross references to the parameters for configuring these services, see "Basic and Additional H.323 Services."
These services include the following features:
The Cisco ATA supports two modes of fax services, in which fax signals are transmitted using the G.711 codec:
How you set Cisco ATA fax parameters depends on what network gateways are being used. You may need to modify the default fax parameter values (see "Configuring and Debugging Fax Services").
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Note Success of fax transmission depends on network conditions and fax modem response to these conditions. The network must have reasonably low network jitter, network delay, and packet loss rate. |
H.323 supplementary services are services that you can use to enhance your telephone service. For information on how to enable and subscribe to these services, see the "CallFeatures" section and the "PaidFeatures" section.
For information on how to use these services, see "Using H.323 Supplementary Services."
The following list contains the H.323 supplementary services that the Cisco ATA supports:
Table 1-1 provides the basic steps required to install and configure the Cisco ATA to make it operational.
Table 1-1 Overview of the Steps Required to Install and Configure the Cisco ATA and Make it Operational
Posted: Wed Jul 9 17:47:28 PDT 2003
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